// Copyright (c) Appeon. All rights reserved.
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. 
// You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0.

using System;
using System.Data;
using System.Data.Common;
using JetBrains.Annotations;
using IBM.Data.DB2.Core;

namespace SnapObjects.Data.Informix
{
    public class InformixStringTypeMapping : StringTypeMapping
    {
        private readonly int _maxSpecificSize;
        private readonly DB2Type? _db2Type;

        /// <summary>
        ///     Initializes a new instance of the <see cref="InformixStringTypeMapping" /> class.
        /// </summary>
        /// <param name="dbTypeName"> The name of the database type. </param>
        /// <param name="sqlDbType"> The <see cref="DbType" /> to be used. </param>
        /// <param name="unicode"> A value indicating whether the type should handle Unicode data or not. </param>
        /// <param name="size"> The size of data the property is configured to store, or null if no size is configured. </param>
        public InformixStringTypeMapping(
            [NotNull] string dbTypeName,
            DB2Type? db2Type = null,
            bool unicode = false,
            int? size = null)
            : base(dbTypeName, GetDbType(unicode), unicode, size)
        {
            _db2Type = db2Type;

            _maxSpecificSize = CalculateSize(unicode, size);
        }

        private static DbType? GetDbType(bool unicode)
        {
            if (!unicode)
            {
                return System.Data.DbType.AnsiString;
            }

            return null;
        }

        private static int CalculateSize(bool unicode, int? size)
        {
            return unicode
                           ? size.HasValue && size < 4000 ? size.Value : 4000
                           : size.HasValue && size < 8000 ? size.Value : 8000;
        }

        /// <summary>
        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
        ///     directly from your code. This API may change or be removed in future releases.
        /// </summary>
        public override TypeMapping Clone(string dbTypeName, int? size)
        {
            return new InformixStringTypeMapping(
                           dbTypeName,
                           _db2Type,
                           this.IsUnicode,
                           size);
        }

        /// <summary>
        ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
        ///     directly from your code. This API may change or be removed in future releases.
        /// </summary>
        protected override void ConfigureParameter(DbParameter parameter, IAdoDbParameter adoDbParameter)
        {
            // For strings and byte arrays, set the max length to the size facet if specified, or
            // 8000 bytes if no size facet specified, if the data will fit so as to avoid query cache
            // fragmentation by setting lots of different Size values otherwise always set to
            // -1 (unbounded) to avoid SQL client size inference.
            base.ConfigureParameter(parameter, adoDbParameter);

            if (_db2Type.HasValue &&
                parameter is DB2Parameter sqlParameter)
            {
                if (_db2Type.Value == DB2Type.NVarChar)
                {
                    sqlParameter.DB2Type = DB2Type.VarChar;
                }
                else
                {
                    sqlParameter.DB2Type = (DB2Type)_db2Type;
                }
            }

            /*var value = parameter.Value;
            var length = (value as string)?.Length ?? (value as byte[])?.Length;

            parameter.Size = value == null || value == DBNull.Value || (length != null && length <= _maxSpecificSize)
                ? _maxSpecificSize
                : -1;*/

            parameter.Size = this.Size ?? -1;
        }

        /// <summary>
        ///     Generates the SQL representation of a literal value.
        /// </summary>
        /// <param name="value">The literal value.</param>
        /// <returns>
        ///     The generated string.
        /// </returns>
        protected override string GenerateNonNullSqlLiteral(object value)
        {
            return this.IsUnicode
                           ? $"N'{this.EscapeSqlLiteral((string)value)}'" // Interpolation okay; strings
                           : $"'{this.EscapeSqlLiteral((string)value)}'";
        }
    }
}
